The field of the invention is soil indicators, and the invention relates more particularly to devices or methods for providing an objective measurement of the degree of soiling of carpets. It is important that a carpet be cleaned before the degree of soiling reaches a very high level so that the carpet may be restored to its original appearance by cleaning. If the amount of soiling is excessive, it is usually impossible to return the carpet to a like-new appearance no matter how often it is cleaned. On the other hand if the carpet is cleaned when it is only moderately soiled, it may be brought to a like-new appearance in most instances and maintained for a far longer period of time with such periodic cleaning. It is difficult, however, for the unskilled person to determine the time or amount of soiling at which the carpet should be cleaned. Laboratory testing utilizing reflectance measurements with a double beam recording spectrophotometer have been run to determine the time or amount of soiling at which the carpet should be cleaned. Laboratory testing utilizing reflectance measurements with a double beam recording spectrophotometer have been run to determine the degree of soiling at which level professional carpet cleaning may restore the carpet to a like-new appearance. It is, of course, impractical to run such test in the average home or office, and there is thus a need for a portable and inexpensive soil gauge which will approximate the results achieved with reflectance measurements utilizing a spectrophotometer.